Brightness monitoring for LED failures and daylighting target adjusting

ABSTRACT

A system monitors operational status of a lighting element. A lighting fixture processor instructs a lighting element to illuminate at a predetermined time, receives sensed light level information from the light sensing element, and transmits a message including information representing the sensed light level. A room controller can control some or all of these steps. A daylighting arrangement includes a room controller that instructs the lighting fixtures of a lighting group to illuminate their lighting elements at a predetermined time of day. Sensed light level information is obtained and transmitted to the room controller, which determines an initial daylighting target for the lighting fixture group based on an average of the sensed light level information. The room controller instructs the lighting fixtures to illuminate their respective lighting elements in accordance with the initial daylighting target.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, claims the benefit of and priorityto previously filed U.S. patent application Ser. No. 15/477,327 filedApr. 3, 2017, entitled “Brightness Monitoring for LED Failures andDaylighting Target Adjusting,” which is a divisional of, and claimed thebenefit of and priority to previously filed U.S. patent application Ser.No. 15/132,624, now U.S. Pat. No. 9,648,697, filed Apr. 19, 2016,entitled “Brightness Monitoring for LED Failures and Daylighting TargetAdjusting,” which are hereby incorporated by reference in theirentirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to lighting control systems,and more particularly to an advanced system and method for monitoringlighting fixtures to detect failures and to adjust daylighting targets.

BACKGROUND OF THE DISCLOSURE

Light emitting diode (LED) lighting fixtures are becoming increasinglypopular due to their advantages over lighting fixtures that employ otherlighting technologies such as fluorescent and incandescent bulbs. LEDlighting fixtures excel in energy consumption efficiency, reliability,and length of lifetime compared to fluorescent and incandescenttechnologies. Additional advantages of LED lighting fixtures, whencompared specifically to fluorescent lighting fixtures, include theability to turn on instantly. Moreover, the lifetime of an LED lightingfixture is unaffected by cycling on and off, such as when powered on andoff during normal usage.

LED fixtures often include a plurality of individual LED elementsmounted on a substrate, with the combined output of the individual LEDelements providing a desired brightness and/or color of light. One issuerelating to such lighting fixtures is that when one or more of theindividual LED elements fail, unwanted changes can occur to the overallbrightness and/or color of the light emitted from the fixture. Suchchanges may or may not be easily observable by the naked eye, makingphysical inspection difficult.

In view of this, attempts have been made to automatically detect when anindividual LED element or a lighting fixture has failed or is failing.In some systems it is common to add circuitry to a device that isproviding power to the lighting fixture to measure the power used. Inthe case of a single lighting fixture, if the power/current is zero, itcan be assumed that the lighting fixture has failed. In the case wherethe device is powering multiple lighting fixtures, if the power/currentis observed to drop significantly it can be inferred that at least onelighting fixture has failed.

In the case of LEDs, failure typically results in the loss of lightintensity (including complete failure in which no light is emitted), butwith continued current draw. For this reason, failure detectiontechniques that employ power monitoring are not effective in determiningLED failures. Thus, testing and troubleshooting fixtures in an LEDlighting control network can be time consuming, often involving asignificant amount of manual labor. Commissioning agents often need toidentify the fixture(s) in a specific room using building layoutdocuments, and then may need to walk to the room and troubleshoot eachlighting fixture in that room. Adding to the complexity is that master(central) controllers used in such systems are often located inelectrical closets or behind ceilings, and it may be necessary toconnect a user input to the master controller which, in turn, requiresaccessing and opening the master controller to connect the user inputthereto.

In addition to the aforementioned problems, when LED lighting fixtures(or individual LED elements) fail, it can impact daylightingfunctionality of the associated lighting system. Since daylightinglevels for a particular space are often set once (e.g., when thelighting system for a room is initially installed), failure of one ormore LED lighting fixtures in a room can adversely affect lightinglevels in the room throughout the day.

In view of these deficiencies in current systems, it would be desirableto provide a system and method for monitoring one or more LED lightingfixtures to automatically determine when intensity changes occur so thatreplacement or repair can be performed quickly and efficiently. Inaddition, it would be desirable for such a system and method to identifythe individual LED lighting fixture that is affected so that amaintenance operations can be directed to the specific fixture,eliminating the need for room walk-throughs. Further, it would bedesirable for the system and method to automatically adjust daylightinglevels when an LED lighting failure is detected, and to readjustdaylighting levels once the affected LED lighting fixture is repaired.

SUMMARY OF THE DISCLOSURE

A system is disclosed for monitoring operational status of a lightingelement. The system may include a lighting fixture including a housing,a lighting element and a lighting fixture transceiver. The lightingelement and the lighting fixture transceiver may be disposed within thehousing. A light sensing element may be provided, and a processorcommunicatively coupled to the lighting fixture and the light sensingelement. The processor may be programmed to: instruct the lightingelement to illuminate at a predetermined time; receive sensed lightlevel information, where said sensed light level information representsinformation obtained by the light sensing element while the lightingelement is illuminated, and said sensed light level informationcomprises a sensed light level value; compare the sensed light levelvalue to a predetermined light level value and; transmit an alert whenthe sensed light level value deviates from the predetermined light levelvalue by a predetermined amount.

A system is disclosed for adjusting a daylighting target for a lightingarrangement. The system may include a lighting fixture group comprisinga plurality of lighting fixtures. Each of the lighting fixtures in thelighting fixture group may comprise a housing, a lighting element, alight sensing element, a lighting fixture processor and a lightingfixture transceiver disposed within the housing. A room controller mayhave a first processor and a first transceiver. The first processor maybe programmed to: instruct, via the first transceiver, each of theplurality of lighting fixture processors to: illuminate their lightingelements at a predetermined time of day; receive sensed light levelinformation from their light sensing elements while their lightingelements are illuminated; and transmit, via the lighting fixturetransceiver, respective wireless messages including informationrepresenting the sensed light level. The first processor may further beprogrammed to receive, via the first transceiver, the respectivewireless messages and to determine a daylighting target for the lightingfixture group based on an average of the sensed light level information,and instruct, via the first transceiver, the plurality of lightingfixture processors to illuminate their respective lighting elements inaccordance with the daylighting target.

A method is disclosed for monitoring operational status of a lightingelement of a lighting fixture. The method may include: instructing, froma processor, a lighting element to illuminate at a predetermined time;receiving, at the processor, sensed light level information, said sensedlight level information representing information obtained by the lightsensing element while the lighting element is illuminated, said sensedlight level information comprising a sensed light level value; comparingthe sensed light level value to a predetermined light level value; andtransmitting an alert when the sensed light level value deviates fromthe predetermined light level value by a predetermined amount.

A method is disclosed for adjusting a daylighting target for a group oflighting fixtures, each of the lighting fixtures including a fixtureprocessor, a lighting element, a light sensing element, and a fixturetransceiver. The method may include: instructing, from a firsttransceiver of a room controller, the plurality of lighting fixtures to,one at a time: illuminate their lighting elements at a predeterminedtime of day; receive sensed light level information from their lightsensing elements while their lighting elements are illuminated; andtransmit, via their lighting fixture transceivers, respective wirelessmessages including information representing the sensed light level. Themethod may further include receiving, via the first transceiver, therespective wireless messages; averaging, by a first processor associatedwith the room controller, the sensed light level information receivedfrom the plurality of lighting fixtures; determining a daylightingtarget for the lighting fixture group based on the average; andinstructing, via the first transceiver, the plurality of lightingfixture processors to illuminate their respective lighting elements inaccordance with the daylighting target.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example, a specific embodiment of the disclosed invention willnow be described, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary lighting system accordingto a first preferred embodiment of the disclosure;

FIG. 2 is a schematic diagram showing the placement and structure of anexemplary entry station according to the lighting system of FIG. 1;

FIG. 3 is a plan view of an exemplary layout of lighting fixtures inmultiple rooms of a building;

FIG. 4 is a logic diagram illustrating a first preferred embodiment ofthe disclosed method; and

FIG. 5 is a logic diagram illustrating a second preferred embodiment ofthe disclosed method.

DETAILED DESCRIPTION

The disclosure provides systems and methods for using a light sensingelement associated with an LED lighting fixture to monitor the fixture'slight output and determine if a failure has occurred or is about tooccur, and/or if a daylighting target should be adjusted. Preferably,the light sensing element is integrated into the LED lighting fixture.

In one embodiment an LED lighting fixture or system may include anoccupancy sensor, a light sensor such as a photocell, and a plurality ofLED elements. The amount of light output by the plurality of LEDelements can be measured by the light sensor when the lighting fixtureis initially installed. A reference value for this initial measurementmay be recorded and saved in memory. Thereafter, the light sensor mayperiodically measure the amount of light output by the LED element, andthe periodic measurements can be compared against the reference value todetect changes which may be indicative of a failure or failing conditionof one or more of the plurality of LED elements.

In another embodiment, a lighting control system may include a roomcontroller and a plurality of LED lighting fixtures, whereby eachfixture is integrated or associated with a power pack module and asensor and control module. For example, the sensor and control moduleand the power pack module may be integrated into the housing of thefixture. This may be particularly useful where the fixture is a trofferor linear fixture. Alternatively, the sensor and control module may bemounted in the ceiling (e.g., a drop ceiling) alongside the fixture,while the power pack may be integrated into or associated with thefixture above the ceiling (e.g., the power pack may be mounted to anexisting electrical box via a knock out). This may be particularlyuseful where the fixture is a recessed lighting fixture. Communicationsbetween the sensor and control module and the power pack may be via aserial cable.

As will be described herein, in use, the room controller may beincorporated into an entry station that includes one or more useraccessible interfaces (e.g., buttons, slides, etc.) for receiving userinstructions. Alternatively, the room controller and the entry stationmay be located in separate and distinct housings. For example, the entrystation may be located adjacent an entrance to a room while the roomcontroller may be located within the ceiling or wall.

As will be described herein, in use, each lighting fixture may includean occupancy sensor and a light sensing element for collectinginformation on the room's occupancy and light levels, respectively. Thelight sensing element may also collect information about light levelsemitted from one or more LED elements of the lighting fixture. Thisinformation may be transmitted to, or otherwise obtained by, the sensorand control module. Using a processor and a transceiver located in thesensor and control module, the information can be transmitted to theroom controller. In some embodiments the room controller may beresponsible for collecting all sensor information from a group oflighting fixtures associated therewith (e.g., a plurality of lightingfixtures located in one or more rooms of a building) and for commandingone or more functions of the lighting fixtures in the group.

Referring now to FIG. 1, an embodiment of the disclosed lighting system1 includes a lighting fixture 2 having a housing 3 within which may bedisposed a lighting element 4 and a sensor and control module 6. In someembodiments the lighting element 4 comprises a light emitting diode(LED) element. In other embodiments the lighting element 4 includes aplurality of individual LED elements. The system 1 may also include apower pack 8 and a room controller 10. The sensor and control module 6may include an occupancy sensing element 12, a status indicator 13 suchas an LED, a light sensing element 14 such as a photocell, and acommunications module 16, which may include a wireless communicationsmodule/chip. The communications module 16 may include a fixtureprocessor 18 and a fixture transceiver 20. Though the fixture processor18 and fixture transceiver 20 are shown and described as separateelements, they may be integrated, for example, onto a single mpu orchip. In alternate embodiments, a separate transceiver can be used inplace of the fixture transceiver 20.

The power pack 8 may be coupled to the sensor and control module 6 viaone or more power and communications cables 22, 24 so that the powerpack 8 can supply power to the sensor and control module 6 (via thepower cable) and so that the sensor and control module 6 can commandoperation of the power pack 8 (via the communications cable). In someembodiments the communication cable is a simple universal asynchronousreceiver/transmitter (UART) connection for messaging between the sensorand control module 6 and the power pack 8. In the illustratedembodiment, the power pack 8 is disposed outside of the housing 3 of thelighting fixture 2. It will be appreciated, however, that embodimentsare contemplated in which the power pack 8 is integrated into thehousing 3. Alternatively, it will be appreciated that although thesensor and control module 6 is coupled to the lighting element 4 viapower pack 8, in various embodiments communications between the sensorand control module 6 and the lighting element 4 may be direct, withoutthe intervening power pack. For example, the sensor and control modulemay communicate directly with the lighting element driver.Alternatively, the sensor and control module may communicate directlywith the lighting element. For example, the lighting element may be aCOB and the sensor and control module may communicate directly with theCOB via an applicable communication protocol (e.g., DMX). Communicatingdirectly with the lighting element or its associated driver eliminatesthe need for the intervening relay or power pack.

The power pack 8 may be coupled to the lighting fixture 2. In addition,the power pack 8 is often coupled to a source of power (e.g., linepower) 26 so that the lighting element 4 may be selectively illuminated.For example, the lighting element 4 may be selectively illuminated inresponse to an occupancy condition sensed by the occupancy sensingelement 12 or a command from the room controller 10. The power pack 8may provide relay switched power for turning the lighting fixture ON andOFF, along with 1-10 Vdc dimmer control for dimming the lights UP andDOWN.

The fixture transceiver 20 may be coupled to an antenna 21 and may useany of a variety of suitable wireless transmission technologiesincluding RF transmission using one of the many standards developed bythe Institute of Electrical and Electronic Engineers (IEEE), infraredtransmission using a standard from the Infrared Data Association (IrDA),or any other standardized and/or proprietary wireless communicationtechnology. A non-limiting exemplary listing of appropriate wirelesstransmission technologies include ZigBee, Bluetooth, Wi-Fi, 802.15.4,near field communication (NFC), Z-wave.

The fixture processor 18 may be communicatively coupled to each of theindividual components of the sensor and control module 6 to control oneor more operational aspects of the lighting control system 1. Forexample, the fixture processor 18 can be communicatively coupled to theoccupancy sensing element 12, the status indicator 13 and the lightsensing element 14 so that the fixture processor 18 can receiveoccupancy detection and light level information. The fixture processor18 also may receive and process incoming wireless messages via thefixture transceiver 20 and may command the transmission of outgoingwireless messages via the fixture transceiver 20. In one particularembodiment, the fixture processor 18 is configured to: (i) receiveoccupancy and ambient light level information from the occupancy sensingelement 12 and light sensing element 14, respectively; (ii) manage thetransmission of occupancy and ambient light level information to theroom controller 10; (iii) receive messages from the room controller 10;and (iv) transmit operational command signals to the power pack 8 tocontrol the lighting element 4. In other embodiments, the fixtureprocessor may send a wireless message to a communicatively coupled entrystation, room controller 10 or other wireless lighting fixture, based onan occupancy condition sensed by the occupancy sensing element 12.

In one non-limiting exemplary embodiment, the communications module 16includes a ZigBee radio. The communications module 16 may be configuredto manage the occupancy and light sensing elements 12, 14 and fortransmitting sensor status to the room controller 10 and for receivingcommands from the room controller 10. A non-limiting example of anappropriate communications module 16 is a Silicon Labs ZigBee system ona chip (SOC) EM3581-RT. The EM3581-RT is a fully integrated SOC thatintegrates a 2.4 GHz, IEEE 802.15.4-2003-complaint transceiver, amicroprocessor, flash and RAM memory.

It will be appreciated that although the lighting fixture 2 is disclosedas communicating with the room controller 10 via a wirelesscommunication link, in some embodiments the lighting fixture maycommunicate with the room controller via a hard wired digital connectionsuch as Ethernet, Power over Ethernet, RS485, CAN, or the like.

The occupancy sensing element 12 may employ any of a variety of sensingtechnologies, including passive infrared (PIR), ultrasound (U/S), audio,video, microwave, and the like (or a combination thereof). In onenon-limiting exemplary embodiment the occupancy sensing element 12 is adigital PPR sensor. The light sensing element 14 may, in onenon-limiting exemplary embodiment, be a 0-10V digital photosensor. Thelighting fixture 2 may be a troffer, a linear fixture, a pendant, arecessed fixture, a wall wash, or the like. As previously noted, thelighting element 4 may comprise at least one LED.

As shown in FIG. 2, and as previously described, the room controller 10may include a first transceiver 32 which may, in one non-limitingexemplary embodiment, may be a ZigBee radio. A non-limiting example ofan appropriate first transceiver 32 is Silicon Labs' model EM358x-RT. Inthe illustrated embodiment and as previously mentioned herein, the roomcontroller 10 can be embodied in a line powered entry station, though itwill be appreciated that other embodiments can include a separate roomcontroller. It will be appreciated that although the processor iscoupled to the AC source of line power 26, in practical application ACpower would not be applied directly to the low voltage components of theroom controller 10. Rather, and for example, at least an AC-DC converterwould be coupled between the source of line power 26 and the firstprocessor 34.

The first transceiver 32 may include a first processor 34, a firsttransceiver portion 36, and a first antenna 46. The first transceiverportion 36 may be communicatively coupled to the first processor 34.Though the first transceiver portion 36 and first processor 34 are shownand described as separate elements, they may be integrated, for example,on a single chip. Non-volatile memory may be associated with the firstprocessor 34.

The room controller 10 may include a second wireless transceiver 38,which in one non-limiting exemplary embodiment is a Bluetoothtransceiver, and more preferably BLE. The second transceiver 38 may beused to communicate with a remote device such as a smartphone, smarttablet, laptop, or other computing device running a custom application(“App”) which can facilitate commissioning, monitoring, remote controland application code updates. An example of an appropriate secondtransceiver 38 is a Texas Instruments BLE chip, such as model TI CC2541or CC2640. The second transceiver 38 may include a second processor 40,and may have a second transceiver portion 42 with a second antenna 44that is separate from the first antenna 46 of the first transceiver 32.In other embodiments the first transceiver 32 and the second transceiver38 may share a single antenna. Though the second transceiver portion 42and the second processor 40 are shown and described as separateelements, they may be integrated, for example, on a single chip.Non-volatile (or other suitable) memory may be associated with thesecond processor.

The first and second processors 34, 40 may be coupled in a manner thatenables them to intercommunicate with each other. A wired communicationcoupling is shown, but this is not limiting. As will be appreciated,such intercommunication can allow information to be passed through thesystem 1 in an efficient manner. For example, a user may, with a remotedevice (e.g., smartphone, smart tablet, laptop, etc.) transmit receiveinformation (e.g., light level information) from the second transceiver38 and second processor 40 via Bluetooth.

As previously mentioned, the disclosed system and method enable alighting fixture 2 to automatically measure the illumination level ofits lighting element 4 to confirm that the lighting element 4 isoperating above a predetermined illumination level, and to alert anoperator if the lighting element 4 is determined to be operating belowthe predetermined illumination level.

In order to determine whether the lighting element 4 of a particularlighting fixture 2 is providing a desired level of illumination, aninitial illumination measurement may be obtained. In some embodiments,the initial illumination measurement is preferably obtained shortlyafter the lighting fixture 2 is initially installed in a targeted space.The initial illumination measurement may be obtained by any means nowknown or hereafter developed. For example, the initial illuminationmeasurement may be obtained using the light sensing element 14integrated into or associated with the lighting fixture 2 that containsthe lighting element 4. In some embodiments the fixture processor 18 maybe programmed to obtain this initial illumination measurement.Alternatively, the initial illumination measurement may be commanded bythe first processor 34 of the room controller 10. Where the initialillumination measurement is commanded by the first processor 34 of theroom controller 10, a wireless message may be sent from the firstprocessor 34 of the room controller 10 to the fixture processor 18 viathe first transceiver 36 and the fixture transceiver 20, whereupon thefixture processor 18 may obtain the initial illumination measurement. Instill further embodiments, the first processor 34 may be commanded toobtain the initial illumination measurement by an operator using aremote device. In such cases an instruction from the remote device maybe received at the room controller 10 via the second transceiver 38.

In one non-limiting exemplary embodiment, the initial illuminationmeasurement may be obtained by the fixture processor 18 commanding thelighting element 4 to illuminate. While the lighting element 4 isilluminated, the fixture processor 18 may obtain a measurement of thelight outputted by the lighting element 4 from the light sensing element14. The fixture processor 18 may store this measurement in non-volatilememory associated with the fixture processor 18. Alternatively, or inaddition, the fixture processor 18 may transmit the measurement to thefirst processor 34 via the fixture transceiver 20 and the firsttransceiver 36. The first processor 34 of the room controller 10 maythen store this measurement in associated non-volatile memory. In someembodiments the initial illumination measurement information may also beprovided to a remote device via the second transceiver 38 of the roomcontroller 10.

In order to maximize the accuracy of the initial illuminationmeasurement, the initial measurement may be obtained at a time of daywhen there is little, if any, external light. In this way, all of thelight sensed by the lighting sensing element 14 can be assumed to beattributed to the lighting element 4 of the lighting fixture 2 underobservation. Thus, in some embodiments the initial measurement may betaken during periods of minimal daylight contribution and no spaceutilization (e.g., nighttime, after working hours). In one non-limitingexemplary embodiment, the initial measurement may take about 5 secondsper lighting fixture.

It will be appreciated that although the disclosed systems and methodsare being discussed in relation to the lighting fixture 2 and roomcontroller 10 of FIGS. 1 and 2, the disclosed systems and methods can beapplied equally to systems in which the occupancy sensing element 12 andlight sensing element 14 are not located within the housing of thelighting fixture 2, but instead are located in the room with thelighting fixture.

Referring to FIG. 3, a particular room may include a plurality ofindividual lighting fixtures 2. Thus, to maximize the accuracy of theinitial illumination measurement for each fixture, it may beadvantageous to obtain the measurements individually (e.g., fixture byfixture), to ensure that the light sensed by the light sensing element14 of each fixture can be assumed to be attributed to the lightingelement 4 of a single lighting fixture. Thus, in some embodiments thefirst processor 34 located in the room controller 10 may schedule eachlighting fixture 2 associated therewith to obtain an initialillumination measurement for its lighting element 4 at a differentdiscrete time. In one non-limiting exemplary embodiment, the lightingfixtures 2 may be instructed, one by one, by the first processor 34 ofthe room controller 10 to cycle their lighting elements 4 and obtain theinitial illumination measurements using their respective light sensingelements 14.

Alternatively, one or more manual techniques may be used to obtain theinitial illumination measurements. For example, the lighting fixtures 2may be provided with a dip switch, toggle or other manual inputmechanism which, when actuated, may initiate the illumination andmeasurement sequence described above for each lighting fixture 2. Inother embodiments the illumination and measurement sequence can beinitiated via wireless communication with a remote device, such as asmartphone, smart tablet, laptop, or the like. In such cases the fixtureprocessor 18 may be programmed to run a routine that, when initiated bythe manual input, turns on the lighting element 4 of the lightingfixture 2, and obtains the initial illumination measurement from thelight sensing element 14 and stores that information in non-volatilememory associated with the fixture processor 18. The fixture processor18 may then turn off the lighting element 4. The operator may go to eachlighting fixture 2 in a particular room, obtaining the initialillumination measurements in a sequential manner. Alternatively, anoperator may only actuate a first lighting fixture 2 in a particularroom to start the process. Once that first lighting fixture 2 hasobtained the initial illumination measurement from its light sensingelement 14 and stored that information in non-volatile memory associatedwith the fixture processor 18, the first lighting fixture may theninstruct a next closest lighting fixture 2 to do the same. Anappropriate wireless instruction message may be sent and received viathe communications modules 16 of the associated lighting fixtures. Inresponse to the received instruction, the next closest lighting fixturemay then turn on its lighting element 4, obtain an initial illuminationmeasure from its light sensing element 14, and store that information innon-volatile memory associated with its fixture processor 18. Theprocess may continue, with each lighting fixture 2 instructing a nextlighting fixture to obtain initial illumination measurements untilmeasurements have been obtained for all of the lighting fixtures in theroom.

In some embodiments the fixture processors 18 may transmit the initialillumination measurements to the first processor 34 of the roomcontroller 10 via the fixture transceiver 20 and the first transceiver36. The initial illumination measurements may be stored in non-volatilememory associated with the first processor 34 and/or they may beprovided to a remote device via the second transceiver 38.

Once the initial illumination measurement has been obtained for thelighting element 4 of a lighting fixture 2, the measurement can then beused as a baseline against which to determine future performance of thelighting element 4. In some embodiments, each lighting fixture 2 may beperiodically tested to determine whether the lighting element 4associated with the lighting fixture 2 is providing a desired level ofillumination. For example, periodic illumination measurements can beobtained for the lighting element 4 of each lighting fixture 2 byperiodically commanding the lighting element 4 on, and obtaining ameasurement of the outputted light using the lighting fixture's lightsensing element 14. The periodic illumination measurements may becompared to the initial illumination measurement to determine whetherthe lighting fixture is operating above a desired level. These periodicillumination measurements can be obtained daily, weekly, monthly,quarterly, or the like based on the clock associated with the lightingfixture or the room controller.

In one embodiment these periodic illumination measurements may beperformed under lighting conditions similar to those under which theinitial illumination measurement was obtained. The periodic illuminationmeasurements may be compared to the initial illumination measurement forthat lighting fixture 2, and where the difference between the initialillumination measurement and a periodic illumination measurement isgreater than a predetermined threshold amount, appropriate action may betaken. In one non-limiting exemplary embodiment, where a comparison ofthe periodic and initial illumination measurements indicates thelighting element 4 has undergone a reduction in illumination of morethan 10%, an alert may be provided to a user so that an operator mayrepair or replace the lighting fixture 2 or the lighting element 4.Examples of such alerts will be described in greater detail below.

The comparison between the initial illumination measurement and theperiodic illumination measurement may be performed by any processorassociated with the system. For example, the comparison between theinitial illumination measurement and the periodic illuminationmeasurement may be performed by the fixture processor 18. In otherembodiments the comparison may be performed by the first processor 34located in the room controller 10. Still further, the comparison may beperformed by a processor associated with a remote device which iscommunicatively coupled to the room controller 10, for example, via thesecond transceiver 38. The periodic illumination measurements can bestored in the non-volatile memory associated with the processor used,such as the fixture processor 18, the first processor 34, both, etc. Thestored illumination measurements can, in some embodiments, be used todevelop trending information. For example, the stored illuminationmeasurements can be used to predict when a particular lighting element 4may be expected to fail (i.e., drop below the predetermined thresholdamount) so that repair or replacement of the lighting element 4 orlighting fixture 2 may be performed before failure occurs.

For embodiments in which the fixture processor 18 performs thecomparison between the initial illumination measurement and the periodicillumination measurement (and where the comparison indicates thelighting element 4 has undergone a reduction in illumination of morethan a predetermined amount), an alert may be transmitted. The alert maycomprise a wireless message transmitted from the fixture processor 18 tothe first processor 34 via the fixture transceiver 20 and firsttransceiver 36. In some embodiments the first processor 34 may then senda wired or wireless message to an operator using a remote device, viathe second transceiver 38. The alert may include information sufficientto identify the individual lighting fixture 2 to which the alertapplies. In some embodiments the alert may include additionalinformation such as an indication that the lighting element 4 of aparticular lighting fixture 2 is approaching the predetermined thresholdamount so that preventive maintenance of the fixture can be performedbefore the fixture exceeds the predetermined threshold amount. In someembodiments the alert can be a physical indicator disposed on theaffected lighting fixture 2, such as illuminating the fixture's statusindicator 13.

In addition to determining whether the lighting elements 4 of individuallighting fixtures 2 are providing a desired level of illumination, thedisclosed systems and methods may be used to set, adjust and resetdaylighting levels for a particular space.

Referring now to FIG. 3, an exemplary layout of a plurality of lightingfixtures 2 within a floor of a building is shown. In this non-limitingexemplary embodiment, a plurality of spaces 30, 30A, 30B, 30C, 30D eachinclude one or more installed lighting fixtures 2 _(1-n), 2A_(1-n),2B_(1-n), 2C_(1-n), 2D_(1-n) and a designated room controller 10, 10B,10C, 10D (with the exception of the light 2A₁ in room 30A, which may becontrolled by room controller of an adjacent room). It will beappreciated that, in the context of the disclosure, the room controller10 (10B, 10C, 10D) can in some embodiments be a larger area controller(e.g., controlling the lighting fixtures in several rooms), or it may bea central controller for a building of which the rooms are a part. Ascan be seen, certain of the lighting fixtures 2 ₁, 2 ₃, 2 ₅, 2 ₉, 2 ₁₀in one of the rooms 30 are located near a set of windows, while other ofthe lighting fixtures in the room are located further away from thewindows. As will now be described, certain of the lighting fixtures inone or more of the spaces may have a daylighting algorithm appliedthereto.

Daylighting (often referred to as daylight harvesting) involves theoperation of lighting fixtures at reduced levels to provide, incombination with natural daylight, a minimum desired level of ambientlighting for an occupied space. Thus, during daylight hours, certain ofthe lighting fixtures in a space may be operated at a reducedillumination level when natural sunlight provides a portion of the totalillumination required for a space. In the evening, when natural sunlightno longer contributes to the illumination of the space, the lightingfixtures may be operated at a higher illumination level, since they maybe the sole source of illumination required for the space.

Daylighting calibrations typically assume that the involved lightingfixtures 2 are capable of operating at the illumination levelsassociated with the initial illumination measurement. Thus, when one ormore of the lighting fixtures 2 emits a reduced level of light becauseone or more of its individual LED elements has failed or is failing, ordue to a change in the room environment (e.g., if the furniture is movedor changed or if new carpet of a different brightness is installed),insufficient light may be provided to the space during daytime hours. Tocounter the effects of one or more underperforming lighting fixtures 2,an automatic daylighting calibration technique can be implemented toset, adjust, and reset daylighting levels to accommodate changes inillumination that can be caused by failed or failing lighting elements,changes to the room environment, or repairs or other changes to lightingelements in the room.

In some embodiments, an initial daylighting target may be obtained.Thereafter, periodic measurements may be obtained from the light sensingelements 14 of a group of lighting fixtures 2 to confirm whether thedaylighting target should be adjusted. The initial daylighting targetcan be determined when the system is first installed. Exemplary methodsfor determining an initial daylighting target, and operating accordingto such a daylighting target, are disclosed in U.S. Pat. No. 7,608,807to Hick et al., and U.S. Pat. No. 8,227,731 to Hick et al., the entiretyof which patents are incorporated by reference herein. The periodicmeasurements can be performed manually or automatically according to anydesired period scheme. Automatic recalibration can also be scheduledwhen a change in measured illumination from one or more lightingelements 4 in a group is determined to exceed a predetermined threshold,as previously described. Automatic recalibration can also occur on aperiodic basis such as monthly, quarterly, semi-annually, annually, orany other desired period.

In one embodiment, initial daylighting calibration may be performed atthe same general time of day as the initial illumination measurementsare obtained (e.g., nighttime, when the space is not being used). In onenon-limiting exemplary embodiment, the room controller 10 may command agroup of designated lighting fixtures 2 to turn on and off together. Alighting group may consist of lighting fixtures 2 positioned adjacent toa set of exterior windows, such as lighting fixtures 2 ₁-2 ₁₃ of room 30(FIG. 3). The fixture processors 18 of each lighting fixture in thelighting fixture group may receive the command from the room controller10, and in turn may command the lighting elements 4 to illuminate. Thefixture processors 18 may then obtain measurements of the lightoutputted by the lighting element(s) using their associated lightsensing elements 14. The fixture processors 18 may store thismeasurement in non-volatile memory associated with the fixtureprocessor. Alternatively, or in addition, the fixture processor 18 maytransmit the measurement to the room controller's first processor 34 viathe fixture transceiver 20 and the first transceiver 36. The firstprocessor 34 may store this measurement in associated non-volatilememory.

The first processor 34 of the room controller 10 may then take anaverage of the illumination measurement information received from eachof the grouped lighting fixtures 2, and may use the average value todetermine an initial daylighting target level. The average value wouldalso be stored in non-volatile memory associated with the fixtureprocessor 18, the first processor 34 of the room controller 10 and/or aremote device. As will be appreciated, during the daytime, a certainportion of that daylighting target level will be contributed by naturalsunlight, and thus, the light provided by the individual lightingelements 4 of the grouped lighting fixtures 2 will be reduced ascompared to their full brightness.

As will be appreciated, changes in illumination from one or morelighting elements 4 in a group can affect the daylighting target levelfor the lighting group (and as mentioned, changes in room layout,furniture and carpet selection can also affect the target level). Toaddress such changes, periodic recalibration of the daylighting targetlevel can be performed. The recalibration may be performed in a manualor automatic fashion. Manual recalibration may be initiated by anoperator manually activating a dip switch, toggle or other manual inputmechanism which signals the fixture processor 18 to begin a calibrationprocess. In other embodiments the manual recalibration can be initiatedby via wireless communication with a remote device, such as asmartphone, smart tablet, laptop, or the like. Automatic recalibrationmay be initiated by the fixture processor 18, the first processor 34 ofthe room controller 10, or by a remote device via the room processor'ssecond transceiver 38. Automatic recalibration can be performed on apurely periodic basis (e.g., daily or monthly based on the clockassociated with the lighting fixture or the room controller), or it canbe event driven. For example, automatic recalibration may be scheduledwhen the comparison between the initial illumination measurement and theperiodic illumination measurement for a particular lighting fixture 2 ina lighting group indicates the lighting element 4 has undergone areduction in illumination of more than a predetermined amount. Suchscheduling may include re-calibrating the daylighting target level(using the previously described technique) at the same general time ofday as the initial illumination measurements are obtained (e.g.,nighttime, when the space is not being used).

The periodic re-calibration technique may be identical to the techniqueused to determine the initial daylighting target level, and changes tothe average illumination value may be used in lieu of the initiallydetermined average value in order to set the recalibrated daylightingtarget level.

As will be appreciated, implementing the disclosed recalibrationtechnique may enable daylighting levels to be automatically adjusted toaccommodate for changes in the space environment. Such changes caninclude reduced illumination levels from one or more lighting fixtures 2in the space (e.g., when one or more fixtures fails or is failing), aswell as increased illumination levels from one or more lighting fixtures2 in the space (e.g., when one or more fixtures are repaired).

In use, shortly after installation, an initial light level value of thelighting fixture is preferably obtained by the light sensing element andstored in memory. Thereafter, periodically, the lighting fixture isinstructed to illuminate. More preferably, the lighting fixture isinstructed to illuminate at night time when the amount of natural lightis expected to be minimal at best. Each time the lighting fixture isinstructed to be illuminated, the light sensing element measures theamount of light. The measured or sensed amount of light is stored inmemory. The sensed light level value is compared to the initial lightlevel value. If the sensed light level value deviates from the initiallight level value by a predetermined amount, an alert is transmitted.The alert may be transmitted to a remote device via a wirelesscommunication link or a hard wired connection such as Ethernet, Powerover Ethernet, RS485, CAN, or the like.

Referring now to FIG. 4, a logic diagram illustrates a first embodimentof the disclosed method. At 1000, a processor instructs a lightingelement of the lighting fixture to illuminate at a predetermined time ofday, preferably at nighttime when no natural light is expected. In someembodiments the processor is a lighting fixture processor disposedwithin a housing of the lighting fixture. In other embodiments theprocessor is a room controller processor that is communicativelycoupled, via a lighting fixture processor, to the lighting fixture. At1100, the processor receives sensed light level information. The sensedlight level information can represent information obtained by the lightsensing element while the lighting element is illuminated, and caninclude a sensed light level value. In some embodiments the lightsensing element is part of the lighting fixture, while in otherembodiments the light sensing element is not part of the lightingfixture but instead is disposed within the room in which the lightingfixture is installed. At 1200, the processor stores the sensed lightlevel information as an initial light level value in non-volatile memoryassociated with the processor. At 1300, the processor again instructsthe lighting element of the lighting fixture to illuminate. Thisinstruction can occur at the predetermined time of day (i.e., the sametime of day at which the initial light level value was obtained). Insome embodiments this step will occur at a future date (i.e., at leastthe next day, week, month or year) as compared to the date the initiallight level value was obtained. At 1400, the processor receives sensedlight level information obtained by the light sensing element while thelighting element is illuminated. The sensed light level information caninclude a sensed light level value.

At 1500, the processor compares the sensed light level value to theinitial light level value do determine if the sensed light level valuedeviates from the initial light level value by a predetermined amount.In some embodiments the predetermined amount comprises a percentagevalue based on the initial light level value. If the sensed light levelvalue does not deviate from the initial light level value by apredetermined amount, then the process returns to step 1300 where, atthe next scheduled interval (e.g., day, month, semi-annual, annual), theprocess repeats. If, however, the sensed light level value is determinedto deviate from the initial light level value by a predetermined amount,then at 1600, an alert is transmitted. For embodiments in which thecomparison step is performed by the lighting fixture processor, thealert may be transmitted to the room controller. For embodiments inwhich the comparison step is performed by the room controller processor,the alert may be transmitted by the room controller to a remote device(e.g., smart phone, smart tablet) via a wireless transceiver associatedwith the room controller.

FIG. 5 is a logic diagram illustrating a second embodiment of thedisclosed method relating to the setting of a daylighting target value.At 2000, a first transceiver of a room controller transmits instructionsto a plurality of lighting fixtures. At 2100, In response to theinstructions from the room controller, the lighting fixtures illuminatetheir lighting elements at a predetermined time of day. At 2200, thelighting fixtures receive sensed light level information from theirlight sensing elements while their lighting elements are illuminated. At2300, the lighting fixtures transmit respective wireless messagesincluding information representing the sensed light levels. At 2400, therespective wireless messages are received via the first transceiver ofthe room controller. At 2500, a first processor of the room controlleraverages the sensed light level information received from the pluralityof lighting fixtures. At 2600, the first processor determines adaylighting target for the lighting fixture group based on the average.At 2700, the room controller instructs, the plurality of lightingfixture processors to illuminate their respective lighting elements inaccordance with the daylighting target. For embodiments in which themethod is performed on a periodic basis (e.g., daily, monthly) themethod may then return to 2000.

Some embodiments of the disclosed may be implemented, for example, usinga storage medium, a computer-readable medium or an article ofmanufacture which may store an instruction or a set of instructionsthat, if executed by a machine (i.e., processor or microcontroller), maycause the machine to perform a method and/or operations in accordancewith embodiments of the disclosure. By way of example, such a machinemay include, but not limited to, any suitable processing platform,computing platform, computing, processing, computing system, processingsystem, computer, processor, or the like, and may be implemented usingany suitable combination of hardware and/or software. Thecomputer-readable medium or article may include, but not limited to, anysuitable type of memory unit, memory, memory article, memory medium,storage, storage article, storage medium and/or storage unit, forexample, memory (including, but not limited to, non-transitory memory),removable or non-removable media, erasable or non-erasable media,writeable or re-writeable media, digital or analog media, hard disk,floppy disk, Compact Disk Read Only Memory (CD-ROM), Compact DiskRecordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk,magnetic media, magneto-optical media, removable memory cards or disks,various types of Digital Versatile Disk (DVD), a tape, a cassette, orthe like. The instructions may include any suitable type of code, suchas source code, compiled code, interpreted code, executable code, staticcode, dynamic code, encrypted code, and the like, implemented using anysuitable high-level, low-level, object-oriented, visual, compiled and/orinterpreted programming language.

While certain embodiments of the disclosure have been described herein,it is not intended that the disclosure be limited thereto, as it isintended that the disclosure be as broad in scope as the art will allowand that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular embodiments. Those skilled in the artwill envision additional modifications, features, and advantages withinthe scope and spirit of the claims appended hereto.

What is claimed is:
 1. A system for adjusting a daylighting target for alighting arrangement, comprising: a lighting fixture group comprising aplurality of lighting fixtures, each of said lighting fixtures in saidlighting fixture group including: a housing, a lighting element, a lightsensing element, a lighting fixture processor and a lighting fixturetransceiver disposed within the housing; a room controller having afirst processor and a first transceiver, the first processor programmedto: instruct, via the first transceiver, each of the plurality oflighting fixture processors to: illuminate their lighting elements at apredetermined time of day; receive sensed light level information fromtheir light sensing elements while their lighting elements areilluminated; and transmit, via the lighting fixture transceiver,respective messages including information representing the sensed lightlevel; wherein the first processor is further programmed to receive, viathe first transceiver, the respective messages and to determine adaylighting target, and instruct, via the first transceiver, theplurality of lighting fixture processors to illuminate their respectivelighting elements in accordance with the daylighting target.
 2. Thesystem of claim 1, wherein the instruct step is performed periodicallyat the predetermined time based on clock information associated with theroom controller.
 3. The system of claim 2, wherein the first processoris configured to perform the instruct step at the predetermined timewhen the first processor determines, from the information representingthe sensed light level, that the sensed light level for the lightingelement of at least one of the plurality of light fixtures is less thana predetermined value.
 4. The system of claim 1, wherein communicationbetween the first transceiver of the room controller and each of thelighting fixture transceivers of the lighting fixture is via a wiredconnection.
 5. The system of claim 4, wherein the wired connection is awired digital connection.
 6. The system of claim 4, wherein the wiredconnection is via one of an Ethernet cable, a Power over Ethernet cable,an RS485 cable, or a CAN cable.
 7. A method for adjusting a daylightingtarget for a group of lighting fixtures, each of the lighting fixturesincluding a fixture processor, a lighting element, a light sensingelement, and a fixture transceiver, the method comprising: instructing,from a first transceiver of a room controller, the plurality of lightingfixtures to, one at a time: illuminate their lighting elements at apredetermined time of day; receive sensed light level information fromtheir light sensing elements while their lighting elements areilluminated; and transmit, via their lighting fixture transceivers,respective messages including information representing the sensed lightlevel; receiving, via the first transceiver, the respective messages;determining, by a first processor associated with the room controller, adaylighting target for the lighting fixture group; and instructing, viathe first transceiver, the plurality of lighting fixture processors toilluminate their respective lighting elements in accordance with thedaylighting target.
 8. The method of claim 7, wherein the firsttransceiver instructs the plurality of lighting fixtures to perform saidilluminate, receive and transmit steps periodically at the predeterminedtime based on clock information associated with the first processor. 9.The method of claim 8, wherein the first transceiver instructs theplurality of lighting fixtures to perform said illuminate, receive andtransmit steps when the sensed light level for the lighting element ofat least one of the plurality of light fixtures is determined to be lessthan a predetermined value.
 10. The method of claim 7, whereintransmitting, via the lighting fixture transceivers, respective messagesand receiving, via the first transceiver, the respective messages isperformed by a wired connection.
 11. The method of claim 10, wherein thewired connection is a wired digital connection.
 12. The method of claim10, wherein the wired connection is via one of an Ethernet cable, aPower over Ethernet cable, an RS485 cable, or a CAN cable.
 13. Themethod of claim 10, further comprising: averaging, by the firstprocessor associated with the room controller, the sensed light levelinformation received from the plurality of lighting fixtures, whereindetermining the daylighting target for the lighting fixture group isbased on the average.
 14. The system of claim 1, wherein the daylightingtarget is a daylighting target for the lighting fixture group based onthe sensed light level information.
 15. The system of claim 14, whereinthe daylighting target for the lighting fixture group is based on anaverage of the sensed light level information.